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How to Get Rid of Engine Noise in Car Stereo

Engine noise in car stereo could mean the difference between a miserable commute that feels endless versus one that feels like you’re traveling with a live band on your dashboard.

Engine noise in the form a high pitch whining that gets louder and higher in pitch as you accelerate is one of the most common problems with car audio systems.

This noise can be introduced into a car audio system by a wide variety of things. That’s the reason why it can be tricky and challenging to hunt down the culprit.

Luckily for you, we’ve compiled a comprehensive list covering all the possible causes and remedies for getting rid of engine noise in your car stereo. Each method is dependent on the cause of the problem, so it’s important that you understand what exactly is going on before you proceed in troubleshooting this problem.

What Causes Engine Noise in a Car Stereo?

Engine noise or alternator whine is one of the most annoying form of noise. It refers to the noise (that sounds like a miniature siren) introduced through the power and ground wires connected to your receiver. This is mainly caused by a big difference in electrical potential (voltage) between two points or by a ground connection that is less than ideal.

If the noise changes in pitch or intensity with engine speed (RPM), it’s probably some type of engine noise, and interference from the alternator output is a likely source.

To get rid of whining noise from speakers when accelerating, you’ll either need to install an alternator noise suppressor on the power line between the battery and the alternator to minimize the problem, or install a noise filter on the receiver’s power cable to cut down on signal interference.

In either case, the noise will still be there, but the filters will most likely prevent it from getting into the head unit and cause the speakers to whine.

Noise in the form of humming, buzzing, or whining can be introduced into a car audio system by a wide range of things. So, if some kind of noise is still audible after installing the filters, then you need to further investigate the issue.

Non-Alternator Engine Noise Problems

It must be noted that most of the components and wires in a car audio system have the potential to introduce unwanted noise. For that reason, it can be really difficult to track down the culprit.

In fact, any of the components can pick up other engine noises that don’t have to do with the alternator. They won’t necessarily be whining noises, but they can be.

To help you hunt down and fix the issue, we’ve compiled an exhaustive list of the most important things you’ll need to check.

1. Ground loop

Ground loops are a major cause of noise, hum, and interference in car audio systems, simply because they’re so easy to create.

Ground loops can happen when multiple devices are connected to a common ground via different paths. The duplicate ground paths form the equivalent of a loop antenna.

Multiple amplifiers, for example, can create ground loop problems, which can usually be solved by grounding each amplifier to the vehicle chassis with a separate wire. However, if you are unable to locate the cause, you can use a ground loop isolator between the head unit’s preamp outputs and the amplifiers to minimize this problem.

It must be noted that ground loop problems can also be caused by mobile devices. This happens when you simultaneously connect your mobile device to your audio system via 3.5mm Aux jack and plugged in to charge via the cigarette lighter.

Ground loop noise caused by mobile devices can be in the form of static, buzz, or whine that changes when you accelerate, and the easiest way to get rid of it is to use a ground loop isolator between the head unit and your mobile device.

2. Improper grounding (loose or intermittent ground connection)

Improper or loose grounding is the number one cause of problems in car audio systems. A bad ground can cause a wide range of problems in a car audio system including but not limited to: whining noise, blowing fuses, weak output, audio clipping, amp overheating, and a host of other issues.

Essentially, what grounding does is that it completes the electrical circuit powering your equipment. A loose or intermittent ground connection will put your audio gear at risk for distortion and noise.

If the ground connection is loose, corroded, or rusted, tighten, clean, or relocate it as needed.

Additionally, if you have an aftermarket receiver, make sure it’s not grounded to the factory ground. The latter is not good enough for aftermarket head units because they are far more sensitive to energy than stock head units.

It goes without saying that anything that generates an electrical field can introduce offending noise into your car’s audio system. So, make sure the receiver’s ground wire isn’t located near a noise source (like a heater, air conditioner, or computer).

The same thing goes for amplifier grounding. So, it’s of paramount importance to make sure your amplifier is properly grounded.

Speaking of which, the best place to have your amp grounded is to the vehicle’s metal chassis, and the grounding point should be sanded down and scraped clean of any paint or primer. This is not to mention the fact that it should be as near to the amplifier’s location as possible, ideally within eighteen inches of the amp location because a long ground wire will put the amp at risk for unwanted noise.

P.S: Check the ground wires to all of the components in your system. This may include the equalizers, crossovers, or other components.

 

On a side note, in order to assure efficient and smooth current flow, make sure the gauge of the ground wire matches the gauge of the power wire.

If the power or ground cables are too small for the amplifier you’re using, the amplifier may experience thermal shutdown because it isn’t getting the power it needs to make the output you want. The amplifier might also drop into protect mode to prevent serious damage.

Use the the chart below as a quick reference in determining the appropriate wire gauge.

Wire Gauge SizeTotal Amplifier RMS Wattage
0/1 AWG1000+ Watts
4 AWG400-1000 Watts
8 AWG200-400 Watts
10 AWG100-200 Watts

3. Poor amp mounting (ex: amp mounted to a conductive surface)

Noise can also be introduced to a car stereo system when an amplifier is mounted to a conductive surface. I mean, if the amplifier case comes in direct contact with the metal of the vehicle, either directly through the case or through the mounting screws touching the chassis, it’ll create a ground loop that results in a whine or hum.

That is why most car amplifiers come with plastic bushings to be snapped into the mounting feet. These bushings are meant to isolate the screw body from the amp chassis.

Another great amp mounting technique is to bolt a wooden board to your vehicle, then secure the amplifier to it. Just make sure the screws securing the amp are not long enough to go through the wooden board and make it to the chassis.

A good rule of thumb to keep in mind in the car audio industry is, if anything metal touches anything metal on the amp, there is a good chance it’ll create offending noise.

4. Bad gain setup

An amp’s gain refers to the input sensitivity adjustment necessary to match the output voltage of the source unit to the input circuit of the amplifier.

In order to enjoy your music’s full range of dynamics and exciting details, your amplifier’s gain must be set correctly. Otherwise, you’ll experience background noise and distortion sounds like speaker crackling, flapping, crunching, or hissing that interferes with the distinct sound of a musical instrument.

Read our detailed article about amplifier gain and how to properly set it up for more information.

5. Long ground wire

A long ground wire is another potential cause of noise in car audio systems. So, the shorter the ground wire the better.

The ground cable should be preferably less than 18″ long, the same exact size (AWG gauge) as the power cable, bolted directly to a solid, thick steel part of the chassis which is sanded down to bare metal, and scraped clean of any paint or primer for best possible grounding.

The reason why it’s recommended to use a short ground wire, is because of resistance. The resistance of a wire is directly proportional to its length and inversely proportional to its cross-sectional area. You can calculate the resistance of a wire by multiplying its length by its diameter. So, a shorter wire will have less resistance.

In other words, as a wire becomes longer, the amount of current it can pull decreases significantly. Therefore, it is recommended to use a shorter ground wire than power wire to ensure that it can ground as much current as is being put into the amp by the power wire.

It must be noted, however, that you’re better off with a long ground wire to a good grounding point, compared with a short ground wire to a poor grounding point.

6. Bad antenna cable

If the noise is only heard when listening to the radio, it may be coming through the antenna. So, remove the head unit, unplug the antenna and check if the noise is still there.

If removing the antenna gets rid of the noise, then the interference is likely being introduced somewhere along the run of the antenna cable.

To fix this problem, you’ll need to reroute the antenna cable so it doesn’t cross or come close to any wires or electronic devices that might introduce interference. You may also need to install an antenna noise suppressor that plugs in between your antenna and the receiver.

If that doesn’t fix the problem or you don’t find any potential sources of interference, you may need to replace the antenna.

7. Bad RCA patch cables

Noise can be picked up by the RCA patch cables connecting your components. This is the reason why it’s important to have excellent audio cables for the best noise rejection.

To check whether RCA patch cables are the source of noise, you’ll need to unplug them from the amplifier, and then insert one side (left or right) of a spare patch cable into the amp’s left and right input jacks. Then, turn on your system and engine.

If the noise is gone, reconnect the cables to the amp, and disconnect them from your receiver. If you hear the noise, your patch cables are definitely picking it up.

What you need to do is to inspect the RCA patch cables for any visible damage in the form of crimping, kinks, tear, or cuts in the insulation. Any wire with the smallest damage must be fixed or replaced.

If the wires are close to a power cable or close to an electronic device, you must re-route them.

8. Detached/Shorted speaker wires

Speaker wires run through the cabin, and connect each speaker to the head unit (or the amplifier).

Noise can also come in through these wires. To test them, switch the engine off and unplug the speaker wires from the amp or head unit. Then start the car. If the noise is still there, then it’s definitely being radiated into the speaker wires.

To fix this problem, inspect the wires for cuts, breaks, frayed insulation or scrapes that expose the copper wire. Any wire with the smallest damage must be fixed or replaced.

If any of these wires is close to an interference source, and you can’t reroute them for whatever reason, try shielding them by wrapping them with Mu-metal foil.

Furthermore, make sure all connections and any wire splices are secure.

9. Worn out or loose speaker

The next thing you need to check when you hear noise in your car audio system is the speakers.

If one of your speakers has bit the dust, you may hear either a crackling sound (especially at high volume levels) or no sound at all.

More often than not, the main reason why your car speakers crackle is because of a bad connection between the source (receiver/amp) and the terminals on the speaker itself.

If your car speakers are crackling, popping, rattling, or produce unusual distortion or distinct buzzing at high volume levels, then you definitely need to check each speaker individually by using the balance and fader controls, or simply by visually inspecting each speaker and making sure there is nothing pressed up against it.

Furthermore, a speaker that is not securely tightened to its housing will vibrate and sound horrible. To get rid of that disrupted sound, make sure the screws are well-tightened, or, as a last resort use foam baffles behind the speakers.

P.S: Sometimes a speaker with minor damage can be easily fixed while other times it can mean having to replace the entire speaker.

 

10. Defective amp/headunit

Last but not least, a bad amplifier, a faulty head unit, or any other defective components such as crossovers and equalizers can also be the source of noise.

11. Problem in the vehicle’s charging system

If everything checks out okay, and you’ve ruled out all the potential causes mentioned above, but you’re still getting noise in the form of static, whine, or hiss, then it’s highly likely that there’s a problem in the vehicle’s charging system. You need to have a mechanic check your alternator and battery.

How to Prevent Engine Noise in Car Stereo

Engine Noise and all other types of noise are easy to avoid if you’re prepared to deal with it. Below, we’ve listed a few tips that’ll help you prevent car audio noise. Follow them and keep your car’s audio system noise free.

1. The best cure is prevention

It goes without saying that the best way to stop noise is to prevent it from occurring in the first place. I can’t emphasize this enough. I mean, if you’ve ever spent an entire day tearing an installation apart in order to eliminate some noise, you’d know what I mean.

So, take all the time you need to sketch your car audio system out before you begin installation. This is especially true if you’re building a complex system or if you’re a relative greenhorn when it comes to car audio.

The graphic representation of your audio system will help you avoid introducing ground loops and will serve as a road map for eliminating noise if it ever comes up.

2. Avoid ground loops like a plague

Ground loops are very easy to create. Therefore, they’re number-one cause of unusual noise in car audio systems. They occur mainly when multiple devices are connected to a common ground via different paths. Loud buzz and annoying hum are some of the most common manifestations of ground loops.

3. Never run signal wires alongside power cables

Power cables naturally produce electromagnetic fields which can interfere with signal integrity in signal wires if they’re installed too closely. For this reason, it’s highly recommended to avoid running signal wires alongside power cables. This is especially true when beefy amplifiers are used.

Powerful amps are notorious for drawing outrageous amounts of power. This power varies greatly depending on how hard you’re pushing the speakers, so does the electromagnetic field surrounding the power cable. The more current flowing through the power wire, the bigger the electromagnetic field gets.

Thus, if signal wires are close to this fluctuating electromagnetic field, the latter could impact the signal quality, causing data loss, or completely disrupt the signal, resulting in poor signal quality and bad signal to noise ratio.

P.S: This also holds true when signal wires are run too closely to strong electrical devices.

 

This brings us to the next point, which is to always use high-quality and well-shielded signal wires to avoid possible interferences.

4. Always use 100% shielded audio cable

Using well-shielded audio wires is mandatory in order to ensure maximum protection against induced noises by power cables and other sources of electromagnetic interference.

5. Never use the OEM ground wire

If your car comes with a ground wire for the car stereo, don’t use it for your new aftermarket receiver.

The OEM ground wire usually makes a very poor ground due to a number of things including its length, small wire gauge, close proximity to other power wires, and unknown termination point.

So, what you want to do is to ground the head unit directly to the chassis or firewall.

6. Make sure your amp has a good ground

There’s no denying that when it comes to amp installation, the ground wire can either make or break your sound system.

The ground for the amplifier should be directed to a bare metal area of chassis of the vehicle, and the grounding point must be scraped clean of any paint or primer, so that the connection is bare metal to bare metal.

7. Keep amplifier power and ground wires as short as possible

Electric cables have a resistance per foot. In other words, the total length of the wire will affect the amount of resistance. The longer the wire the greater its resistance.

P.S: Larger cables have less resistance per foot than smaller cables.

 

According to Ohm’s law, when current is flowing through the resistance, it results in a voltage drop. (voltage = current x resistance). For this reason, it’s of paramount importance to make your power and ground wires as short as possible, and always use the right wiring kit for your amp.

The ground spot must be as near to the amp’s location as possible – ideally within eighteen inches of the amp’s location.

8. Set amp gain correctly

Setting your amp’s gain is a critical part of the installation process. If it’s done correctly, maximum system signal to noise ratio can be obtained.

As mentioned above, the purpose of the gain control is to match the head unit’s output voltage to the gain structure of the amplifier.

There are many different ways to adjust the gain controls of your amplifier including:

  • Adjusting Gains by Ear: This is the fastest and easiest method for adjusting system gains. Best of all is that it’s FREE.
  • Adjusting Gains by Multimeter: This is the most cost effective ways to adjust system gains with predictable accuracy.
  • Adjusting Gains by Oscilloscope: This is what you should be using if you’re into car audio competition. It’s the most accurate ways to adjust system gains. The downside, however, is that Oscilloscopes cost and arm and a leg making this option out of reach for most people.

9. Noise filters are not a real solution

Noise filters are not as efficient. At best they will only reduce the noise, not completely eliminate it. Noise filters aren’t usually required if everything is installed properly

How to Get of Rid of Engine Noise in Car Stereo — Step By Step

If you’ve already installed your stereo system and are unfortunate enough to be dealing with some noise, here’s a detailed step by step process for getting rid of it.

The following steps must be carried out only while the engine is on; this is because engine noise is only produced when the engine is running.

  1. Turn the volume all the way down on the receiver.
  2. Turn the gain up on the amp until engine noise / alternator whine starts to kick in in a big way
  3. Unplug all of the RCA cables from the amplifier.
    1. If the noise is gone, then it must have been produced before the amplifier. In other words, the noise is either coming from the head unit or it’s induced by the RCA cables.
    2. If the noise is still there, then either the amp is what’s causing it or that it’s being induced by power cables that are very close to the speaker wires. In such case, it’s necessary to reroute the power cables away from speaker wires. With the RCA cables still unplugged, double check to make sure there are no shorts between the speaker leads and the chassis of the vehicle. A shorted speaker wire that’s making intermittent contact with the chassis will create a ground loop by establishing a second ground reference point. Thus, if you do have a short, trace the wire out and repair it.
  4. If you’ve made it here, you know that the amplifier and speaker wiring are fine.
  5. Now, plug the RCA cables back into the amplifier, and unplug them from the head unit.
    1. If the noise is still there, the RCA cables are the culprit.
    2. If the noise is gone, the head unit is to blame
      P.S: It should be noted, however, that any other accessories that sit between the head unit and the amplifier such as an equalizer, or crossover, could also be causing the noise.
  6. What you want to do next is to pull out the wires connecting the head unit to the amplifier and place them over the carpet and seats.
    1. If the noise is gone, your RCA cables are undoubtedly what’s causing the noise. As we’ve mentioned above, RCA cables can pick up electrical noise when they’re run close to the amplifier’s power wire. To prevent this from occurring, run the RCA wires on the opposite side of the vehicle from the power wire and avoid running them near any antennas or antenna cables. A switch to shielded, twisted RCA cables can help with the interference if the noise is being induced along the cable run.
    2. If the noise is still there, then your RCA cables need to be replaced.
  7. Last but not least, you may need to re-ground the headunit. So, find a spot, preferably on the chassis, sand it down to bare metal and ground the black wire from the head unit’s harness to the metal surface.
    1. If the noise goes away, then the head unit just needed a better ground.
    2. If the noise is still there, then you may want to want to purchase an inline power filter and/or a ground loop isolator.
      P.S: Ground loop isolators are cheap and easy to install but they do not always help. They may even cause a small loss in your system’s sound quality. Inline power filters on the other hand will only work when the power wires pick up interference and transfer it to the head unit. However, the only way to find if an in line filter can get the job done is to buy it and try it.
  8. Finally, check your amplifier’s grounding point. If the ground point isn’t anything to write home about, you’ll simply need to find a better ground location for the amp. Clean, bare chassis metal is the best solution. The ground wire should be the same gauge as the power wire, and the best ground is the shortest ground.
    1. If the noise goes away, then the amplifier just needed a better ground.
    2. If the noise is still present, either the amplifier is defective and needs to be tested, or that there’s a problem with the vehicle’s charging system.

Alex Brown

Hey There, my name is Alex Brown, I'm an LA-based sound engineer with over 10 years experience installing, troubleshooting, and repairing commercial, automotive, and household sound equipment. I've installed highly competitive car audio systems, and everything from navigation systems to full car stereo systems, remote starters, alarms and beyond. I enjoy creating solutions and simplifying everyday needs. I also love helping people get great sounding gear, thereby, saving the world from bad sound one customer at a time.

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